Showing papers in "Electronics and Communications in Japan Part I-communications in 1987"

An interactive fuzzy satisficing method for multiobjective nonlinear programming problems with fuzzy parameters

Abstract: The fuzziness induced in the decision making in the actual system in general, comprises fuzziness in the formulation of the problem and that in the judgments of the decision maker (DM) as a human being. This paper proposes an interactive fuzzy satisficing method, which takes into consideration the fuzziness in problem formulation as well as that in the judgments of DM. The multiobjective nonlinear programming problem containing fuzzy parameters is transformed into the α -multiobjective nonlinear programming problem. After determining the fuzzy goal of DM for each objective function by eliciting the membership function, the following reference values are set: the fuzziness index α of DM for the fuzzy parameter; and the reference membership values, which are reference for the membership functions. For the specified α and the reference membership values, the corresponding augmented minimax problem is solved, and DM is supplied with the α-Pareto optimal, together with the trade-off ratios among membership functions and the trade-off ratios between α and the membership functions. Obtaining the result, the DM takes the information concerning current α-Pareto optimal solution and the trade-off ratios into consideration, and respond by updating the reference membership values and the value of α if necessary. In this way the satisficing solution finally is derived for DM, thereby ensuring the α-Pareto optimality. This is the proposed interactive fuzzy satisficing method. The interactive process is demonstrated for a numerical example by the interactive computer program.

Reflecting characteristics of anisotropic rubber sheets and measurement of complex permittivity tensor

Abstract: It is well known that rubber sheets mixed with carbon particles or carbon fiber usually exhibit large surface anisotropy due to the rolling process employed in fabrication. The use of such materials for special microwave applications requires measurement of the complex permittivity tensors. However, no reliable method for this purpose in such lossy anisotropic materials has been established. In this paper the reflection loss of anisotropic sheet materials is measured and a method for obtaining complex permittivity tensors from the experimental results is given. That is, the frequency characteristics of the reflection loss are measured for various polarization directions of incident waves at the sheet materials and each element of the tensors including nondiagonal ones can be estimated by the least squares method using these data. As a result of study of the principal direction of the sheet using measured values of this tensor, it is found that the real and imaginary parts differ largely in the principal direction for some of the rubber sheets with carbon used for this measurement.

A rearrangement algorithm for three‐stage switching networks

Abstract: In the three-stage rearrangeable switch-ing network, an internal blocking can occur. However, such a blocking can be eliminated by rearranging the already set-up paths, and thus the network can satisfy any connection requirement. To eliminate this internal blocking, a successive rearrangement of more than one already set-up path is required. The sequence of the paths to be rearranged can clearly be represented by extending the notion of the connection chain introduced by Gotoh. This paper presents a sufficient condition for the Internal blocking to be eliminated by the rearrangement in the extended connection chain, which is a basis for the rearrangement algorithm. It is also verified that the rearrangement algorithm proposed by Gotoh satisfies the sufficient condition. Based on these results, a connection chain is shown in which the internal blocking can be eliminated by the rearrangement. The algorithm to search for the connection chain and to perform the rearrangement is presented. Compared with past methods, in the proposed method, a fewer number of paths is distorted. The usefulness of the method is examined by a simulation.

All digital phase‐locked loop with a wide locking range

Abstract: The phase-locked loop (PLL) is used widely in communication engineering as one of the key functions Recently, some attempts have been made to construct a digital circuit for the phase-locked loop However, the common problems in those attempts is that there is a trade-off between the locking range and the output phase jitter To solve this problem, this paper proposes a new structure for the phase-locked loop with a wide locking range by combining the frequency control technique For this purpose, a new digital VCO is constructed, which can vary the central frequency of the system using the programmable divider and the adder Theoretical analyses are made for the transient behavior from the viewpoints of the locking range, frequency and phase, and the noise characteristics of the loop The result is compared with the results of experiment and simulation The theoretical value, experimental value and the result of simulation agreed well, indicating that the phase-locked loop has a wide locking range

Multiport power combining transmitter for multibeam satellite communications

Abstract: A multiple beam power combining transmitter which has the flexibility to adapt beam power to varying beam traffic is proposed. The new multiport power combining network consists of a power-dividing multiport directional coupler, multiple amplifiers and a power-combining multiport directional coupler. The multiport directional coupler consists of multiple quadrature hybrids. Since each amplifier commonly amplifies signals to each beam, the power allotment to each beam can be changed with flexibility. The concept and configuration of the multiport directional coupler which divides and combines input signals are described. Also, the effects of uneven gain and phase distribution or failure of amplifiers are represented theoretically. Implementation to 8-or 10-beam systems is shown. Finally, the characteristics of the 8-port experimental transmitter utilizing 1.5W FET amplifiers and branch line type hybrids are shown.

Mullis–Roberts–type approximation for continuous–time linear systems

Abstract: As lower-order approximation methods for discrete-time linear systems, Mullis and Roberts have proposed two methods: the so-called modified least-square approximation (MLSA), and the interpolatory approximation (IA). The characteristics of the two methods were investigated considering their relationships. In this paper, a lower-order approximation method for continuous-time linear systems is presented in a form corresponding to MLSA, with its property, algorithm and state-space representation discussed in correspondence with the discrete-time case. The approximation can also be regarded as corresponding to IA, and thus the proposed method is called the continuous-time Mullis-Roberts-type approximation (CMRA). The latter half of this paper presents a formulation for the limiting case (as sampling time 0) from a lower-order approximation method for discrete-time systems to one for continuous-time systems. Thus it is shown that CMRA is obtained as a common limit of MLSA and LA, thereby providing a physical interpretation to the formal correspondence between CMRA and MLSA/IA.

Loop antenna with a branch wire for circular polarization

Abstract: This paper reports on the analysis and design of a circularly polarized antenna consisting of a loop antenna with a branch wire of an appropriate length. The idea for developing this antenna derives from the fact that the branch wire has a characteristic as a transmission line coupled with a loop conductor. The present structure is a simple single-feed antenna operating equivalently as a two-point feed-loop antenna. The current distribution in the antenna is decomposed to the balanced and unbalanced modes for which the equivalent circuit and equivalent loop antenna have been derived. The condition for circular polarization has been obtained from the equivalent loop antenna. Based on this condition, a circularly polarized antenna has been designed and various characteristics such as the axial ratio have been obtained. From these characteristics it is found that a structure exists for which the axial ratio can be made much more broadband than other antennas with the length of about one wavelength. The validity of the theory has been confirmed by experiments.

Improvement of algorithm using interval analysis for solution of nonlinear circuit equations

Abstract: This paper describes an improvement of the solution by Krawczyk, Moore and Jones (KMJ algorithm) for nonlinear equations based on the interval analysis. When the KMJ algorithm is applied to practical problems such as the determination of the operating point of a multistable electronic circuit, a large computation time is required. The reason for the large computation time is as follows: (i) The existence of the solution is determined using the direct-replacement type interval extensions of functions, which enlarges the search region for the solutions; (ii) the region partitioning is repeated until a region X is obtained such that K(X) ⊆ X, where K(X) is Krawczyk's interval function and X is the interval region. The situation is demonstrated by an example. As a solution for these problems, the following method is proposed. (1) The given initial region is partitioned into subregions, and some subregions are excluded from consideration if the solution is judged as nonexistent by the interval extensions of functions; (2) when K(X) ⊆ X, does not apply, the region X is partitioned into XC δ X - (K(X) ∩ X) and XK ∩ K(X) ∩ X, and the KMJ algorithm is applied to XC and XK to examine the existence of the solutions. Finally, as a computation example, the KMJ algorithm with the above two elaborations is applied to the nonlinear circuit equations with two to four variables. It is demonstrated that the computation time can be reduced considerably with the original KMJ algorithm.

Statistical design method of loss budget for the optical subscriber transmission system

Abstract: In the transmission system for the trunk lines, where a high reliability, ie, a severe loss requirement is imposed, the worst condition is usually assumed in the design for the individual gain and loss of the transmission devices and media In this paper this method is called the worst-case transmission loss budget method or the worst-case design Although this method is reliable, it often contradicts the economical requirement in the subscriber transmission system This paper proposes a design method for the transmission system, called the statistical loss budget method or statistical design method Here, the transmission characteristics of the devices and media are assumed to follow statistical distributions with certain ensembles, and assuming that included statistical phenomena are always independent, the transmission performance is secured at a certain level with the specified danger level (significance level) By the proposed statistical design method, the economical requirement can be satisfied while maintaining the overall transmission performance of the system In the optical transmission system, where the transmission loss is less compared with the metallic system, it is a great advantage of the statistical design method that the transmission length can be increased In the design example where the statistical method is applied to the design of an optical subscriber transmission system, the transmission length is increased to approximately 18 times compared with the worst-case design

Role of formant frequencies and bandwidths in speaker perception

Abstract: This paper considers the relation between the vocal tract characteristics under the personality of speech. A pitch synchronous analysis-synthesis system was constructed in which the formant frequencies and the bandwidths can be modified independently. The speech was synthesized by controlling these parameters in natural speech, and an experiment was made on the discrimination of personalities. As a result, it is seen that the personality is strongly sensitive to the formant frequency shift, especially to the shift of the lower three formants, and it is lost by the uniform shift of 5 percent. On the other hand, the personality is well preserved for the change of formant bandwidth, and is sensitive to the bandwidth change in the fourth- and higher-order for-mants. In the case of uniform change of the bandwidth, deformation of wider than 5 times or narrower than one-fifth times completely eliminates the personality.

Numerical analysis of diffraction from a sinusoidal metal grating

Abstract: Diffraction of plane waves by a metal grating of a sinusoidal cross section is investigated theoretically by considering a finite conductivity of the material. The analysis is based on the mode-matching method with a smoothing operation. The numerical results of the diffracted power from a sinusoidal gold grating are presented with sufficient accuracy for both P-polarization and S-polarization. The results have been compared with those for perfectly conducting gratings. It is found that: (i) the reflected power is reduced due to loss compared to the perfectly conducting case, and the acuteness of the anomalous diffraction phenomenon called Wood's anomaly is decreased; and (ii) another anomaly called plasmon anomaly is observed in the case of P-polarization. The latter cannot be observed in a perfect conductor.

Reflection of surface acoustic waves from gratings on the surface of piezoelectric substrates

Abstract: To apply grating reflectors to surface acoustic wave resonators, it is necessary to have knowledge about the reflection characteristics as a function of the grating parameters. This paper discusses the reflection of the surface acoustic wave by the grating composed of periodic metal-strips on a piezoelectric substrate. The surface wave incident upon the grating is reflected by electrical and mechanical surface perturbations due to the strips. The reflection characteristics are analyzed by the perturbation theory and the coupled mode theory, considering the two perturbations. By numerical calculation, it is shown that the manner of superposition of the two perturbations depends on the material of the substrate, the cut-angle and the strip material. For LiNbO3, LiTaO3 and quartz substrates, the calculated value is compared with the experimental values reported elsewhere indicating good agreement.

Unified analysis of ridge-waveguide slot antenna in three-dimensional space and time

Abstract: Recently, there has been much interest in research and development of a high-power heating system for nuclear fusion plasma heating. Since these systems deal with high power, there are several problems that are different from those in the sources for communication systems. A structure is proposed which is based on the T-type ridge waveguide, a simple and sturdy configuration. In these systems, the complex near field due to the three-dimensional structure including the medium conditions has a significant effect on the characteristics. Especially, in a high-power system, the effect of higher-order modes with relatively small power distributions cannot be neglected. Also, transient field distributions strongly affect the characteristics so that the time domain response must be analyzed. This paper applies an analysis technique for the three-dimensional space and time based on the Bergeron method to the systematic analysis of the radiated near field from the entire system of a T-type ridge waveguide slot antenna including the waveguide, slot and the heating regions. The power distribution of the field determining the fundamental properties of the heating system is found in terms of the Poynting vector and the fundamental properties of the system are obtained. Specifically, the effect of the dielectric material on the field distribution is found. The cutoff characteristics of the ridge waveguide and the fundamental properties of the slot are studied and their characteristics are investigated.

A low–loss 6–pole canonical dual–mode filter for the output multiplexer of broadcasting satellite transponders in the 12–GHz band

Abstract: This paper describes the development of a filter for the channel multiplexer in the 12-GHz band broadcasting satellite transponder with a high transmitting power (above 200 W). The filter for high-power multiplexer must have a very low loss, to maintain the satellite transmitting power and to secure thermal stability. It was found that the use of a 6-pole elliptic filter is better than that of a 4-pole elliptic filter from the viewpoint of the insertion loss and the heat dissipation. The 6-pole canonical filter is designed using TE113 dual-mode. In the thermal design, super-invar with small thermal expansion coefficient is used for the cylindrical waveguides of the filter, and copper with high thermal conductivity is used for the iris plate. Improving the heat dissipation and suppressing the temperature-rise, the deterioration of the filter characteristics caused by the temperature variation is prevented. The experimental filter realized the insertion loss of less than 0.3 dB, the loss variation of 0.1 dBp-p and group-delay variation of 5 nsp-p within the channel. No significant deterioration of the filter performance was observed through the thermal test of 0°C to 90°C and the high-power test of 200 W. As a result, it was demonstrated that the proposed filter has better electrical and thermal performance than the previous 4-pole elliptic filter, being suited as the filter for the multiplexers in high-power broadcasting satellite transponders.

Systolic decoder for reed‐solomon codes

Abstract: This paper proposes the systolic decoder for Reed-Solomon (RS) codes based on systolic algorithms. Three steps of decoding procedures for RS codes can be reduced to simple repetitive algorithms and thus can be realized by one-dimensional systolic arrays, each operated by simple controls. The decoding system is a cascade connection of these cell arrays in one dimension. In this paper we also design three types of cells building arrays for RS codes on GF(28). Each cell has a size that permits its integration in a one-chip LSI and we can determine the number of cells according to the error correcting ability for codes.

Performance of a coded 8PSK modem with a viterbi decoder using simplified metric calculation

Abstract: Recently, there has been increased interest in coded octal phase-shift keying (8PSK) modulation for satellite communications, in which convolutional encoding and Viterbi decoding are combined with 8PSK modulation and demodulation. The problem in this paper is how to simplify the process of metric calculation in a Viterbi decoder and realize reduced hardware complexity and increased operating speed of a coded 8PSK modem. An analytical expression is introduced for the performance of a coded 8PSK model with such a simplified Viterbi decoder. The expression is then applied to a typical coded 8PSK modem employing the Ungerboeck code of rate 2/3 and with constraint length ν=2. Effects of simplifications in the Viterbi decoder on the bit error rate (BER) performance of the model have been evaluated. Results in this paper would be useful in the design of future coded PSK modems, since it enables a designer to assess the tradeoffs involved in the simplifications and to realize modems with reduced hardware complexity for highspeed applications.

Adaptive vector quantization of picture signals in discrete cosine transform domain

Abstract: This paper proposes the adaptive discrete cosine transform coding with vector quantization (adaptive DCT-VQ), as a highly efficient coding for the picture signal. In the proposed method, the vector quantization is performed by applying the discrete cosine transform to the picture subblock and partitioning the transformed domain into several vectors. By regarding the transformed domain as more than one vector, the complexity in the coding is reduced. Each vector quantizer is designed according to the standard probability distribution of the cosine transform coefficient, and the universality of the vector quantizer is realized. The mode-selecting type adaptive control is introduced, to effect the adaptive control of the coding parameters according to the local property of the picture. To cope with the large bit allocation resulting from the adaptive control, each vector quantizer has two-stage structure thereby reducing the coding complexity. As a result of the performance evaluation by simulation, it was verified that the proposed coding method has a higher performance than the conventional adaptive cosine transform coding and has much less complexity than the vector quantization in the original space domain.

Radiation characteristics of reflector antenna with radome at 10∼30 GHz in rainy conditions

Abstract: The increase in radome loss, sidelobe levels, and cross-polarization level in the rain plays an important role in determining antenna characteristics. These effects have been investigated at 10 GHz ∼ 30 GHz with a reflector antenna having a planar radome, and a new method has been propsoed for deriving the radome loss in which a water-shedding property of the radome is taken into account. Raindrops on the radome form water streams that flow down onto the surface thereby increasing the loss of the vertical polarization wave. It is also found that the cross-polarization level generated by a wet radome is less than −40 dB. The sidelobe level is not increased and the paraxial radiation pattern is not changed by a wet radome but it is lowered as a whole. In the present theory, the contact angle of a raindrop surface with a radome surface determines the condition of the wet radome surface and this angle was predicted theoretically by using measured radome loss.

A proposal for searching for electromagnetic wave sources by using a synthetic aperture technique

Abstract: Unwanted electromagnetic waves radiated from equipment making use of electromagnetic energy create numerous societal problems. The prevention of these problems has been studied extensively. In this paper, a method for estimating the location of the unwanted electromagnetic waves is studied. Since it is difficult to make the antenna aperture large especailly at low frequencies, a search for electromagnetic wave source via a synthetic aperture technique is proposed. In the estimated electromagnetic source distribution by this method, images similar to the antenna sidelobes appear. It is demonstrated by computer simulation that the images can be suppressed by use of the synthetic aperture method with subarrays or use of Mill's cross method. Discrepancies between the true source location and the estimated location have been found in regard to the synthetic aperture length and the geometrical relationship with respect to the aperture center. It has been found that the antenna configuration with the synthetic aperture length of 10 λ can estimate an electromagnetic wave source within 10 λ square with accuracy of less than 1/4 λ square. Therefore this method is sufficiently practical if the location of the source is restricted somewhat.

Crosstalk noise analysis of wiring on the printed circuit board

Abstract: Recently, progress in the high-density wiring technique on a printed circuit board (PCB) has been remarkable. Thus the problem of malfunctions due to crosstalk noise occurring on the signal line must be addressed. The authors have been developing the noise estimation system for PCB named NESSY and a program to calculate the capacitance of multiconductor system (CALCAP). In NESSY, the wiring pattern is divided into small segments, which comprise the equivalent element circuit. The partial capacitance of the printed pattern is calculated by solving the integral equation and using the image method in CALCAP. The crosstalk analysis of equivalent circuit was made by the circuit simulation program. Among the results of this analysis, crosstalk noise using the partial element equivalent circuit (PEEC) agrees quite well with the measurement. The crosstalk noise should be anticipated by the close coupling theory in the case of frequently used wiring (both the width of signal line and line spacing are less than 1 mm). The crosstalk noise voltage was relatively large in the case of impedance mismatching. The far end crosstalk noise, previously neglected in most cases, becomes especially large.

A new image data compression method–extrapolative prediction–discrete sine transform coding (in the case of one–dimensional coding)

Abstract: This paper proposes the extrapolative prediction-discrete sine transform as a new highly efficient coding for the gray-level image In the proposed method, an extrapolative prediction is made from the immediately preceding pixel to the present pixel block, and the prediction error signal is encoded by the orthogonal transform Assuming that the information source for the image is a stationary first-order Markov process in the wide sense, it is shown that the orthogonal transform which decorrelates the prediction error signal can be approximated by a certain kind of sine transform An algorithm is presented for the high-speed execution of this data The rate-distortion characteristic is discussed for the case of one-dimensional coding, and it is shown theoretically that the coding efficiency of the proposed method is nearly the same as those of the discrete 16-pixel cosine transform with block length of 4 pixels and the 8-pixel fast Karhunen-Loeve transform Comparing the coding complexities of those methods, the proposed method is shown to be especially advantageous in the hardware realization Computer simulations were made for actual images using the fixed-rate coding and variable-rate coding (entropy coding), and the result supports the idea

Data compression and statistical inference

Abstract: When mutually correlated data are observed at two different places, it may happen that data are compressed independently, losing the correlational information as a whole. Such cases are observed frequently in economical and environmental data. When the compressed data (statistics) are combined to perform a statistical inference concerning the probability structure governing the two observations, the loss of the statistical information due to the independent data compression should be noted. In other words, a problem arises of estimating Fisher information lost by the independent data compression in the sense of Shannon information at the two sites. It is another problem to determine the best ways of data compression and estimation. This paper introduced anew the notion of mutual Fisher information, and answers those questions by a new theory, combining the information and the statistical theories. The usefulness of the information geometry, which works on the geometrical structure of the probability space, is also indicated through the discussion.

Suppression of ground clutter using an X‐band radar

Abstract: Most of the clutter received by an L-band air route surveillance radar obeys Weibull distribution with various values of the shape parameters. The L-band radar has a frequency of 1.3 GHz and pulsewidth of 3 μs. Hence, the spatial resolution is as large as 450 m. The X-band radar, on the other hand, ns. frequency of 9.4 GHz and pulsewidth of 80 ns. The spatial resolution is as small as 12 m; we have found that the clutter amplitude distribution obeys a composite Weibull distribution when reflectors are ordinary terrain and such structures as buildings. Clutter suppression techniques for Weibull and non-Weibull echos are proposed.

Some location problems on grid graphs

Abstract: Numerous works have been reported on the facility location problem to minimize or maximize various objective functions for the locations of one or more facilities on graphs. A general approach to these problems is algorithmic, but solutions are seldom found in an explicit manner. By restricting the object graph to grid graphs, this paper gives solutions in an explicit manner to the center problem and the median problem which are fundamental in facility location problems. Strictly speaking: (i) we derive the relationship between the center and median of general graphs G1 and G2 and the center and median of the product graph G1 x G2; then (ii) we find a multicenter and multimedian of the path graph Pn on n vertices and from the results, solve a kind of multicenter and multimedian problem for grid graphs; and (iii) we solve a distance minimization problem on grid graphs.

On routability for channel routing problem

Abstract: The routing requirement in the channel routing problem for automatic wire routing in the interior of LSI is realizable if the constraint graph contains no cycle. Otherwise, the trunks for several appropriate nets must be divided into pieces. In this paper we modify a routing requirement with cyclic conflicts into one without them by dividing trunks into two parts. First we define a directed bipartite graph G to represent the routing requirement. A set of vertices in a strongly connected component in G is called a crowded set. It is shown that a routing requirement is realizable if there exists no crowded set in G. On the other hand, in the presence of a crowded set we define a method of dividing a net n contained in the crowded set into two subnets n' and n'' at some terminal position. If n' and n'' are not contained in any crowded set in the graph modified by division, we say that the division is effective. We then present a necessary and sufficient condition for the existence of effective division. Further, a semi-effective division is defined to deal with the case where there is no effective division and then the routability for the channel routing problem is discussed.

In‐house wireless optical digital SSMA

Abstract: With the recent development of the office automation, portable in-house terminals for data communication have attracted attention. For this purpose, wireless transmission by optical link is considered promising, since it does not require the installation of signal lines. The past discussions and experiments, however, considered only the one-to-one or one-to-many communications, but many-to-many, i.e., multiple connections were not considered. This paper aims at the application of the spread-spectrum system to the wireless optical communication link to realize the multiple connections, and derives the basic theoretical expressions for the receiver characteristics. More precisely, the modulation scheme is selected taking the restriction into consideration, which is inherent to the inhouse wireless optical link. Then, the receiver error rate and the multiple connection characteristics of the proposed modulation scheme have been theoretically derived, providing the basis for the system design. Finally, a qualitative discussion is made on the construction and operation of the synchronous system for the proposed modulation scheme.

Stable power‐combining mode operation of a cylindrical cavity multiple‐device oscillator

Abstract: Presented in this paper is a discussion of the output power combining capability and the stable operation of the desired mode in a cylindrical cavity multiple-device oscillator, in which several devices are placed inside a cylindrical cavity to combine the output of all devices by way of coupling with the TM020 mode of the cavity. A lumped element equivalent circuit is first derived that has the fundamental characteristic of the oscillator structure. From the modal analysis based on this equivalent circuit, it is found that the oscillation output as the sum of the available powers of individual devices can be obtained in principle at TM010 and TM020 modes. It is also noted that the TM020 mode cannot be a stable mode when it is chosen as the desired mode and the TMm10 mode (m ≧ 1) is generated as a stable rotational or standing wave mode. Then we discuss the method of loading the resistor for suppressing unwanted modes in which only the desired output combining mode is stable. Finally, an eight-device oscillator with a simple structure fabricated for trial is used in experiments of power combining and unwanted mode suppression and the results of the analysis of the modal analysis are qualitatively confirmed.

Reflecting characteristics of lossy anisotropic materials inserted into the rectangular waveguide

Abstract: It is known that a large anisotropy exists in the plane of a rubber sheet composed of rubber mixed with carbon fibers or carbon particles with a subsequent pressing by a roller. This anisotropy can be used for fabrication of microwave absorbers and shielding materials. For this objective it is necessary to measure the complex permittivity tensor of these materials. The standing wave method in a rectangular waveguide has been extended for an application of measurement of tensor materials. The analysis of the reflection coefficient is studied for a short-circuited waveguide containing an anisotropic lossy material. If this reflection coefficient can be found, a least square method may be applied to the measured data to determine the tensor component. In this paper, for the analysis of hybrid mode propagating in the anisotropic material, a set of generalized transmission equations is used. For each hybrid mode calculated by this method, the mode matching method is applied to find the reflection coefficient. The calculated results by this method are compared with the measured data. It is found that the agreement is excellent even if the direction of the rolling during the fabrication and that of the electric field are different. It is confirmed that the present method can be applied to the measurement of the permittivity tensor.

Accurate analysis of δv/v surface acoustic waveguides on a piezoelectric anisotropic substrate

Abstract: This paper presents an accurate analysis for the Δv/v surface acoustic waveguide, which is generally applicable to the anisotropic substrate. This is a three-dimensional boundary-value problem in the anisotropic semiinfinite piezeoelectric medium, and includes a number of difficult points for analysis. There are two contradictory requirements for the analysis: (1) flexibility in the object of analysis; and (2) a simple program for numerical computation and small computational complexity. There has not been presented a method which satisfies both these requirements. The method presented in this paper is highly practical, providing a reasonable compromise between the two. The method is as follows. The boundary condition on the substrate surface of the guide is replaced by an integral equation using Green's function. The resulting equation is converted into a matrix equation by partitioning the boundary into elements for discrete representation. Then the eigenfrequency of the guide is determined by solving the equation numerically. The usefulness of the proposed method is demonstrated by the result of numerical calculation for the dispersion characteristics and the field distribution of the guided mode.

Optical switching networks using tree-structured waveguide optical switches

Abstract: To make a large-sized optical matrix is an important subject in realizing optical switching systems. Although optical matrices using waveguide optical switches have potential from the viewpoint of high speed and circuit integration, they are limited in the number of input/output terminals (up to between 4 and 8) due to the insertion loss and multiple crosstalk noise. To reduce these disadvantages, this paper offers optical switching networks using tree-structured N x 1 waveguide switches as fundamental elements. Approximated equations for the insertion loss and the multiple crosstalk are given and it is shown that those in the proposed networks are approximately proportional to the number of stages in the tree structure. A 4 × 4 optical highway switch using Ti:LiNbO3 tree-structured directional couplers was tested to confirm its switching capability. The experimental results obtained have a good agreement with the equations of the insertion loss and the multiple crosstalk characteristic. By using these equations, the size of the realizable switching system was estimated; a highway switch having 32 to 64 terminals is found to be possible with the present technology.